The role of ZrN capping layer deposited on ultra-thin high-k Zr-doped yttrium oxide for metal-gate metal-insulator-semiconductor applications.

Metal-gate MIS structures with and without ZrN capping layer on high-k Y2O3:Zr/Y2O3 stack were fabricated. The binding energies and depth profiles were investigated by x-ray photoelectron spectroscopy (XPS). The x-ray diffraction (XRD) patterns were compared. It is found that Ti out-diffusion into Zr-based high-k dielectric becomes lesser with the insertion of ZrN capping layer. The electrical properties of current-voltage (I-V) and capacitance-voltage (C-V) characteristics were measured in the postannealing temperature range of 550-850 °C. According to the defect reaction model, Zr cation vacancies are associated with the concentration of Ti ion by a transition from +3 to +2 states. The amount of Zr cation vacancies is quantified and equal to a half of Ti substitution amount at Zr site. The reduction in cation vacancies at high temperatures can well explain the decrease in ΔVFB for samples with ZrN layer. In contrast, an excess of Ti outdiffusion will produce the interstitial defects in high-k films without ZrN capping. [ABSTRACT FROM AUTHOR]